Sludges valorization

Concern about the waste recovery increases at industrial level. One of the waste that presents the greatest problem is the sludge generated in the different production processes. The treatment of these is complex and carries a high cost. In addition, your final destination is limited.
It also stands out the increase in its production at the level of Spain, being approximately 975 tons in 2009 and reaching almost 1,300 tons in 2020. Therefore, it is necessary to find a way to give a second life to this type of waste and introduce it in the cycle of the circular economy.
In today’s blog we tell you everything you need to know about sludge and the different ways to add value to it.

What is circular economy?

Until now, the most widespread practice with everyone around us is to use and throw away. Little by little, society becomes aware of the new model based on the idea of ​​extending the useful life of a product or waste as much as possible, thus giving it a value and keeping it within the economy for as long as possible. In this way we reduce the generation of waste.
This model, known as the circular economy, is based on the following principles:

• Eco-conception: considers the environmental impacts that a waste or product has throughout its life cycle.
• Industrial and territorial ecology: it establishes a way to organize the industry within the same territory, optimizing the management of stocks and flows of materials, energy and services.
• Economy of “functionality”: it rewards the implementation of a system of rental of goods, that is to say, that the product, once its main function is finished, returns to the company, which will be in charge of dismantling it and reusing the valid parts.
• The second use: products that no longer correspond to the initial needs of consumers are reintroduced into the economic circuit.
• Reuse: reuse certain waste or products that still retain their functionality for the production of other products.
• Repair: being able to give a second life to defective or damaged products.
• Recycling: take advantage of intrinsic materials in waste.
• Recovery: use energy from waste that cannot be recycled.

This approach makes ATRIA look for “other lives” to the different wastes that are generated at an industrial level, such as sludge.

What properties do the sludge have?

Sludge is usually extremely liquid, with a water content of more than 95%. Their composition varies depending on where the water that originates them comes from (urban or industrial) and the characteristics of the treatment techniques.

Urban origin sludge:

They originate in human activity, which is why organic matter and a great variety of suspended or dissolved matter will stand out in their composition, among them, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) stand out. and magnesium (Mg) which gives it positive properties for its future recovery. Although they can also contain pathogens and organic pollutants.

Industrial origin sludge:

The sludge that originates from industrial activities, in addition to the components of urban sludge, may contain heavy metals such as cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn). Which makes it difficult to revalue it because a more exhaustive treatment is needed before looking for an alternative life.

The composition of the sludge is important to determine if it is a hazardous waste or not, which determines the management that these require.

Sludge applications

According to the State Waste Management Framework Plan (PEMAR) there are two main ways of valuing the generated sludge, both at an industrial and urban level, the application in soils and the generation of energy.

Soil application

This option is the most desirable and relatively simple to apply since the sludge usually has the right substances to promote plant growth.
The application of these sludges on the ground improves the physicochemical and biological properties of this, due to the contribution of the main nutrients (N, P, K) and of humidity and organic matter.
On the other hand, it reduces runoff, preventing soil erosion. Also, the use of fertilizers originating from sludge reduces the use of chemical fertilizers, which means reducing the risk of contamination by the nitrates they release. However, before supplying the sludge to the ground, it is necessary to verify compliance with the laws that govern this field of application.

Energy generation

To generate renewable energy, a biological process is necessary that consists of the anaerobic digestion of sludge. This treatment generates as by-products combustible gases (natural gas or methane) that can be used as an energy source.
This process requires continuous maintenance, since, for it to be carried out, certain bacteria are needed to digest the sludge. These bacteria need certain environmental characteristics that must be monitored daily.

Other lives

• Incineration: Most of the accumulated sludge is eliminated. However, they generate waste such as ash or tar, which must be taken to landfill. In addition, it has the disadvantage that it requires a significant energy supply.
• Landfill: Availability must be checked prior to disposal of sludge.

Projects carried out by ATRIA

At ATRIA we are very aware of the environment, therefore, we look for solutions to avoid the impact on it.
Below, we show you different projects that involve the application of the circular economy:

Agricultural by-products for packaging

In this project the objective was to develop a new material from a by-product of agricultural origin. To achieve this, the final product was characterized, its properties were studied and it was compared with other commercial products.

Extraction of biostimulant compounds

The objective of this project was to obtain compounds with biostimulant capacity from plant by-products for use in agriculture. To do this, an extraction process was designed from the vegetable by-product and the optimal conditions were adjusted. The characteristics of the biostimulants were evaluated and bioassays were carried out in real plantations, studying the growth improvement produced by the biostimulant.

Do you want to apply the circular economy in any of the by-products of your process? Contact us and we will advise you on the best way to reuse.